1. Field of the invention
The present invention relates to a system for checking a production process procedure in a many-kind variable-amount production line including a plurality of production processes, and more specifically to a production process procedure checking system for discriminating an inconvenient sequence in the production process procedures on the basis of a previously prepared knowledge base, and a system for making or preparing a production process flow in a many-kind variable-amount production line.
2. Description of related art
In the many-kind variable-amount production line including a plurality of production processes, the production process procedure for each product kind have become long and complicated, and therefore, a support system for precisely and quickly making or preparing a complicated production process procedure in the production line, is demanded. In addition, if the production process procedure prepared for each individual product kind is checked by a human operator, a long time is required, and a checking error is inevitable. Because of this, a system for automatically checking the production process procedure prepared for each individual product kind, is also demanded.
Now, an example of a prior art process flow preparing system will be described with reference to the accompanying drawings.
FIG. 1 illustrates the example of the prior art process flow preparing system. The shown prior art process flow preparing system includes a code management table 20-5 including process codes each indicating an individual unitary process by a plurality of digits of alphanumeric characters, an attribute management table 20-6 including process conditions each indicating a condition of each individual unitary process, a variable manager 20-4 coupled to these tables, a data selector 20-1 coupled to a variable manager 20-4 for selecting necessary information or data from the tables through the variable manager 20-4, a data display 20-2 coupled to the data selector 20-1 for displaying the data selected by the data selector 20-1, and a data storage unit 20-3 coupled to the data display 20-2 for storing the data.
In preparing or creating the process flow, the process codes and the process conditions are selected in accordance with the production procedure to be made, so as to prepare a flow of the selected processes, and a finally completed process flow is stored in the data storage unit.
When the process flow completed once is modified, and when a new process flow is created, as shown In FIG. 2, the completed process flow is copied, and the process code and the process condition to be added are selected, and then, added to the copied process flow. When a process is removed, similarly, the completed process flow is copied, and the process code and the process condition to be removed are selected, and then, removed from the copied process flow.
Japanese Patent Application Pre-examination Publication No. JP-A-5-266029 (an English abstract of which Is available from the Japanese Patent Office, and the content of its English abstract is incorporated by reference in its entirety into this application) discloses one example of the process flow preparing system for preparing the process flow as mentioned above. In addition, Japanese Patent Application Pre-examination Publication No. JP-A-6-176994 (an English abstract of which is available from the Japanese Patent Office, and the content of its English abstract is incorporated by reference in its entirety into this application) discloses a production process procedure checking system for discriminating whether or not the prepared process flow is suitable. For reference, the contents of JP-A-5-266029 and JP-A-6-176994 are substantially included in U.S. Pat. No. 5,495,417 (the content of which is incorporated by reference in its entirety into this application), since U.S. Pat. No. 5,495,417 claims the Convention Priorities based on applications of JP-A-5-266029 and JP-A-6-176994.
The production process procedure checking system as disclosed by JP-A-6-176994 has an object of quickly checking a long and complicated process flow. For this purpose, the production process procedure checking system has a function of grouping one process to another process as one package, and then checking whether or not there exists a process which is indispensable in the package, whether or not there exists a process which never exists in the package, whether or not there exists a process which is indispensable when a certain process exists.
FIG. 3A illustrates the prior art production process procedure checking system disclosed by JP-A-6-176994 and therefore by U.S. Pat. No. 5,495,417. Here, only portions relating to the present invention will be described. This system includes a package checker 831, a package condition management table 833, a check decision unit 857 and a check management table 859. Under the instructions from the check decision unit 857, while referring to the package condition management table 833, the package checker 831 checks whether or not processes included in each package is normal.
FIG. 3B illustrates the content of the package condition management table 833 included in the prior art production process procedure checking system shown in FIG. 3A. The package condition management table 833 includes, for each one package, the name of the process constituting the package concerned (PROCESS (A), PROCESS (B)), the name of the process indispensable in the package concerned, the name of the package that never exists in the package concerned, the name of the process which is indispensable when a certain process exists (SPECIAL PROCESS), and an error code. In the example shown in FIG. 3B, a thermal oxidation process is never allowed to exist between a lithography (PROCESS (A)) and a resist removal (PROCESS (B)). Therefore, if the thermal oxidation process exists, it is notified that the package is not normal (the error code "005)).
However, the following problems have been encountered in the above mentioned prior art technology.
A first problem is that when the process flow is copied and the process codes and conditions for a plurality of processes are added to or removed from the copied process flow, it is not possible to completely avoid the possibility of an input error. The reason for this is that, for example, when a plurality of processes are added to or removed from the process flow composed of several hundred processes, a correlation with a succeeding process cannot be immediately checked.
In this connection, it may be considered that after the process flow is prepared in accordance with the method disclosed by JP-A-5-266029, the process flow thus prepared is checked in accordance with the method disclosed by JP-A-6-116994. In this case, however, if a portion to be modified is found out after the checking is finished, it is necessary to repeat the checking after making the modification. As a result, a large processing time becomes necessary.
A second problem is that, since a new process flow is prepared by utilizing a copy of the process already prepared, respective process flows for a plurality of different kinds become different in fine process flows, with the result that there occurs the possibility that a suitable process flow cannot be developed for all kinds of products by modifying the equipments in the production line. The reason for this is that, when a plurality of process flows are copied and when the original process flows include a process flow which does not match with an actual situation of the production line, a necessary modification may be omitted unless the process flow designer is aware of the situation forgotten.
A third problem is that, if the condition are selectively inputted for the selected process code as In the method disclosed by JP-A-5-266029, a code input often needs: a long time. The reason for this is considered that, since the process code indicating the process name and the condition code are inputted separately, when there is long process flow, a long time is required for inputting the condition codes, one by one.
In the prior art production process procedure checking system disclosed by JP-A-6-176994. the checking is conducted for each individual process, on the basis of the individual process name and a before-and-behind relation (context) of the individual process name concerned. Therefore, an inference time becomes extremely long when the production process procedure includes several hundred processes, and the knowledge base required for the checking correspondingly becomes voluminous, wit the result that maintenance becomes difficult.
Furthermore, in the prior art production process procedure checking system disclosed by JP-A-6-176994, since the checking is conducted on the basis of the before-and-behind relation (context) of the individual process name as mentioned above, when an attempt is made to insert an additional process into a portion where the arrangement sequence of processes are determined to some degree in the production process procedure, there is possibility that the insertion of the additional process is not inhibited. As a result, the arrangement sequence of processes and the name of processes cannot be made common in various production process procedures.